Does IQ = IQ? Comparability of Intelligence Test Scores in Typically Developing Children

Numerous intelligence tests are available to psychological diagnosticians to assess children's intelligence, but whether they yield comparable test results has been little studied. We examined test scores of 206 typically developing children aged 6 to 11 years on five German intelligence tests (Reynolds Intellectual Assessment Scales; Snijders Oomen Nonverbal Intelligence Test; Intelligence and Development Scales; Wechsler Intelligence Scale for Children, 4th edition; Culture Fair Intelligence Test Scale 2), which were individually administered. On a sample level, the test scores showed strong correlation and little or no mean difference. These results indicate that the tests measure a similar underlying construct, which is interpreted as general intelligence. On an individual level, however, test scores significantly differed across tests for 12% to 38% of the children. Differences did not depend on which test was used but rather on unexplained error. Implications for the application of intelligence assessment in psychological practice are discussed.